1. Field of the Invention
The present invention relates to a piezoelectric bulk-wave resonator that uses the thickness-shear mode and, more specifically, to a piezoelectric bulk-wave resonator in which a single-crystal LiNbO3 substrate is used.
2. Description of the Related Art
Various thickness-shear mode piezoelectric resonators have hitherto been proposed for bulk waves generated by a substantially strip-shaped piezoelectric body. For example, Japanese Unexamined Patent Application Publication No. 4-222108 discloses a thickness-shear vibrator in which a LiNbO3 single crystal is used.
Japanese Unexamined Patent Application Publication No. 60-113511 discloses a thickness-shear resonator in which a LiNbO3 single crystal taken from an about 165°±5° rotated Y cut is used. The Euler Angle representation of this about 165°±5° rotated Y cut is about (0°, 75°±5°, 90°).
As described in these publications, various thickness-shear resonators in which a single-crystal LiNbO3 substrate is used have hitherto been proposed. However, the frequency difference between the resonant frequency and the anti-resonant frequency of such known resonators, namely the band width, is not very broad, making it difficult to prepare wide-band filters.